Fire fighting turnout garment generally consists of three separate layers. Each layer is designed for a specific function related to firefighter safety and comfort. The outer most layer is commonly known as the outer shell. The outer shell, generally a fabric having high flame and tear resistance qualities, is coated for water resistance and increased wear life. The middle layer is generally a breathable fabric known as a moisture barrier. Generally, the moisture barrier layer is a breathable membrane applied to a suitable substrate fabric to achieve a durable and washable moisture barrier layer. The breathable membrane allows moisture to pass from an inner liner fabric. This allows the garment to breathe during fire fighting operations. The inner most layer or thermal liner fabric is generally made with light weight, bulky fabrics to provide thermal insulation from convective and conductive heat. Many thermal liner fabrics also readily absorb moisture from street garments or station uniforms. This three-layer ensemble is typically made to at least the quality standards specified under the NFPA 1971 Standard on Protective Ensemble for Structural Fire Fighting, 1997 Edition.
Generally, outer shell fabrics are made from high-heat and flane resistant fibers such as Basofil(copyright) (melamine), Nomex(copyright) (meta-aramid), Kevlar(copyright) (para-aramid), P-84(trademark) (copolyimide), PBI(copyright) (polybenzimiazole), PBO (poly-p-phenylenebenzobisoxazole), Carbon and Technora(copyright) (para-aramid) and Kynol(trademark) (phenol) or a blend thereof. One commonly used fabric is made from a blend of 40% PBI(copyright) (polybenzimidazole) fibers and 60% Kevlar(copyright) (para-aramid) fibers. PBI(copyright) (polybenzimidazole) fiber is used for its resistance to high heat and flame and para-aramid fiber is used for its high strength and wear resistance properties. Generally, the outer shell fabrics are produced from staple fibers made into ring-spun yarns, however, it is also known to use certain filament yarns. Most outer shell fabrics range in weight from 7 to 8 oz./yd2 and are made from ring-spun yarns in a cotton count ranging from 14/2 to 22/2. The fabrics are typically woven in common weave patterns, such as plain or twill, and include a rip-stop weave in the pattern. The rip-stop weave provides tear resistance and still provides suitable tensile properties.
Outer shell fabrics made from a blend of 40% PBI(copyright) (polybenzimidazole) and 60% para-aramid yield a tan-caramel shade because PBI(copyright) (polybenzimidazole) fiber is naturally dark brown and para-ararnid is naturally lemon yellow. These fabrics have been known for high flame and thermal resistance values, and are also very forgiving of dirt and grease accumulated during use. This recognizable shading and performance in fire service use have made this type and color of fabric almost universally accepted. These types of fabrics are commercially available from Southern Mills of Atlanta Ga., DIFCO, Montreal Quebec; and Safety Components Fabric Technologies, Inc., Greenville S.C. Outer shell fabrics made from other fibers, such as 100% meta-aramid fiber and blends of meta-aramid and/or para-aramid fibers, are dyed to this recognizable shade so they have a similar appearance and are quickly recognized as fire fighting garment material. Color aside, each of these other fabrics may offer different thermal protective properties while still meeting the NFPA qualifications.
The dyeing of meta-aramid and/or para-aramid fabrics is a high-temperature, high-pressure dyeing process that requires skillful processing. However, it has been found that the dye bath chemicals and the mechanical agitation of the fabric during the dyeing process considerably weakens it. In general, the process of piece dyeing aramid fabric is very complicated and costly. Also, the dyed fabric shade differs considerably from one lot to the other. Still further, piece dyed fabric frequently yields poor shade consistency from the jet-dyeing process which results in poor quality, and the showing of xe2x80x9crope marksxe2x80x9d and xe2x80x9ctire tracksxe2x80x9d running along the fabric. As these marks are very visible, these fabrics are generally sold as seconds at a much lower value. This loss of goods or inventory reduction increases the total unit cost of acceptable production. All of the above combine with the loss of fiber from the fabric during dyeing, which can amount to as much as ten percent (10%) of the fabric weight, as motivation to seek a better, more consistent dye process and end product.
It is possible to dye the yarn prior to weaving. However, fabrics produced using this technique are very costly and also involve the same dyeing problems. In addition to dye machine capacity, which often means that yarn dyeing is done in small batches, the nature of the process and the greater loss of fiber from the yarn, which can approach twenty-five percent (25%), cause yarn dyed costs to be much higher than the cost of piece dyeing. This results in higher costs per pound of finished product.
Solution dyed fibers are also available, however, this method is of limited value as most fiber producers offer very little selection in colors. Because solution dyed fibers are commonly at least twice as expensive as natural fibers, this option is rarely used.
The last theoretical option is to stock dye the fiber. However, due to the high-temperature requirements for stock dyeing equipment and the color shade quality of the dyed aramid fiber, this technique is not preferred.
As a result of the above, the majority of the commercial outer shell fabrics are piece dyed using a high-pressure jet-dyeing machine. With the introduction of Basofil(copyright) (melamine) fiber into the fire service industry, efforts have been made to piece dye a blended melamine/para-aramid fabric using the conventional piece dyeing technique. However, this process requires close monitoring because the melamine fiber has a tendency to separate during the process. Attempts to dye ring-spun yarn made from forty percent (40%) melamine and sixty percent (60%) para-aramid fibers resulted in poor quality in the dyed yarn. There was also a weight loss of melamine fiber which amounted to almost thirty percent (30%) during the yarn dyeing process. These problems of poor dye quality and fiber loss argued against stock dyeing of high temperature fibers. However, the inventor""s prior success in using melamine fibers in protective applications, see U.S. Pat. No. 5,496,625 which uses natural fibers, lead to further investigation of using stock dyeing of the melamine fiber prior to blending with a companion fiber to produce outer shell fabrics. The resulting yarn and fabric quality and improved loss control with the stock dyed aramid fiber was surprising in light of the known problem. Recently, it was learned that solution dyeing of melamine makes the fiber brittle, which when spun into a yarn results in greater fiber lost, unacceptable product and increased cost.
As a result of experimental work, a dark brown or chocolate colored stock dyed melamine fiber was produced. Using forty percent (40%) of this chocolate color melamine fiber and sixty percent (60%) of naturally yellow para-aramid fiber, a ring-spun yarn having a tan to caramel color was produced. Using this yarn for the weaving of an outer shell fabric produced an on loom fabric of the desired color and eliminated the need for a piece dyeing process.
A textile yarn suitable for use in protective garment fabric. The yarn is formed from stock dyed melanine blended with fibers selected from the group consisting of aramid fibers, phenolic fibers, flame retardant cellulosic fibers, polybenimldazole fibers, and partly or filly oxidized PAN (polyacrylonitrile) fibers.